Remote tachometer drive



June 10, 1947. P. F. BECHBERGER 2,422,067

REMOTE TACHOMETER DRIVE Filed Dec. 31, 1945 INVENTOR.

firm; F HEL'HBEREE'H BY Patented June 10, 1947 ATEN assess? tsherger ""1 e 41 themes.

The present eating systems synchronous 51 Many system to voltage and; however with. and aircraft speeds indo e t... uring one Another e drive adap eter or the ii motor rseeiv in shmoidm'w derived and n comm whereby 5 volts.- motor the f trioai iiii' J adapted reiativei as to he tive hiehee s voltage to able s oe The shot of the Z31 em; hereinafter fr description W detaiied on "together with the acoompehyi in one embodiment of the invention is ted. It is to he expressiy understood. however, the drawin: is for the purpose of iiiustrrttion oniy and is not designed as a definition of the limits of the Invention. Reference for this iatter purpose should be had to the appended claims.

Referring now to the single figure of the drawing in which one of the various illustrative embodiments of my invention is shown, ili designotes a commutator having four conducting segments II, II, I3 and H, fixed to a shaft I! ro- TAQHQMETER DRIVE Temfly, N.'J., asslgnor to t; 1943, Serial No. 515,444

(@110 lit-274) segments II and it are, mtereenneeted by a r 95, while the'alternate segments 52 and is iiizewise interconneeted by a wire it. trushes l8, l9 and 2&6 spaced 12W apart about the cieriphery of the commutator it? are to ooaot therewith.

. hes being connected 1 a battery 25.,

Mixed to the out ding 21 of a sue IE2 and it. e

is connected its wile thence by v 516. of the rotor Windir to the slip ring 222 n the wire i6 interoomzeeting; events II and i3.

e winding M3 is con ush 28, while the Wii 0 other er; s

connected by lends stator windings oi moment magnet rotor other end of said sh lit having a second permanent il'ifi ilt rotor 36. T se is adapted to he within a com rotor 45 and the cup iii constitute a vice 43, weli knovm in the art.

The cup 41 is integral wi h one end oi $39, the other end of said shaft being more with a pointer lit. The winter so is adapted be moved by said shaft over the face oi. a to indicate the speed of rotation of the shaft A coil spring 52 wound about the shaft to an commutator i8 and the battery 28 are provided to insure a voltage of sumcient amplitude to drive the motor 0. Upon rotation of the shaft it by an engine, the direct current applied to the slip rings 2| and 22 will be inverted by the commutator III to an alternating current having an approximate square wave form. The rotational speed of the shaft It will determine the frequency of the battery current, the amplitude of which will remain constant.

Thus, at very low speeds, a voltage is applied to the stator windings 42 of sufficient amplitude to drive the rotor 4| for operating the drag cup 48. The frequency at which the motor 48 will operate is determined by the frequency of the shaft IS. The alternating current developed by the generator 28 when shaft I5 is rotated at a slow rate of speed, will be extremely small causing very little effect on the battery circuit. It is apparent that the frequency of the battery current as delivered by the commutator will be of the same frequency and phase as the alternating current developed by the generator 28. This is true since the commutator l8 and the rotor winding 21 of the generator are rotated by the shaft IS. The two voltages will, therefore,

be added to each other in the leads 4! to increase the amplitude of the voltage supplied to the mo tor 88.

As the speed of the shaft l5 increases, the generator 28 will eventually develop a voltage of sufficient amplitude to operate the motor 48. As the speed of shaft l5 increases, the voltage developed by the generator increases proportionately, the frequency also increasing. The alternating battery voltage being added to that developed by the generator as the speed increases forms a part of the overall amplitude supplied to the synchronous motor 40. The motor 40 isthus operated at a speed which is at all times proportional to the speed of the shaft I5; at low rates of speed the motor being controlled by the alternating battery current as delivered by the commutator HI, and at higher rates of speed by the A. C. voltage of the generator 28 added to the alternating battery voltage.

There is thus provided a novel drive for electrical tachometers or the like, wherein a relatively accurate measurement of speed in response to frequency supplied is maintained from very low to very high speeds. Also, the present invention eliminates substantially all mechanical speed take-oil connections, is simple to manufacture and easy to install.

While only one embodiment of the invention has been illustratedand described, other changes and modifications, which will now appear to those skilled in the art, may be made without departing from the scope of the present invention. Reference is, therefore, to be had to the appended claims for a definition of the limits of the present invention,

What is claimed is:

l. A remote drive means for a polyphase motor and an indicator element associated therewith, comprising a source of direct current, a plurality of contact members connected to said source, a field winding connected in parallel with said contact members, means adapted to rotate said contact members and said windings simultaneously, and a plurality of stator coils in series with each of said contact members, whereby rotation of said contact members at low speed provides voltage for producing a driving torque to said motor, independently of said winding, di-

4 rectly through said stator coils, and whereby said stator coils have torque producing voltage induced therein at high speeds to drive said motor, which merges with and increases the voltage produced by said contact members.

2. An electrical drive for a polyphase motor comprising a source of direct current, a commutator for converting current from said source to alternating current, a synchronous motor connected in series with said commutator for receiving alternating current therefrom, a generator having field windings rotatable simultaneously with said commutator and connected in series with said source and inparallel with the input side of said commutator, said'generatcr having its generator windings connected in series with said commutator and said synchronous motor. whereby voltage for providing driving torque in said synchronous motor is maintained at relatively low speeds of said commutator, and higher voltage is developed in said generator for driving said synchronous motor, the voltage generated by said generator merging with and increasing the voltage delivered from said source through said commutator.

3. An electrical drive for a polyphase motor, comprising, a polyphasc motor, a source of direct current, a generator having field windings supplied from said source, a commutator having segments connected in parallel to said field windings and connected to receive current from said source, commutator brushes connected in series with the stator windings of said generator and with said polyphase motor, and means adapted to rotate said commutator and said field windings simultaneously, said commutator supplying alternating current from said direct current source to said polyphase motor through said generator windings at sufficient voltage to operate said polyphase motor at low speeds of said rotating means the voltages generated by the rotation of the field windings at higher speeds providing increased voltages to operate said poly-' phase motor at higher speeds.

4. Means in combination with a rotatable shaft for measuring the rotational speed thereof, comprising a, D. C. voltage source, a commutator connected across said D. C. source and rotatable by said shaft, an A. C. generator having a field winding connected across said D. C. source and rotatable by said shaft, and stator coils connected at one end to the output of said commutator; and a synchronous motor connected to the other ends of said stator coils, the A. C. output of said REFERENCES CITED .The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 683,235 Thury Sept. 24-, 1901 814,380 Lamme Mar. 6, 1808 1,068,111 Crain July 22, 1918 1,196,494 Tiffany Aug, 28, 1818 1,196,516 Canton Aug. 28, 1916 

